A novel method has been developed to quantitatively measure cell size from the photomicrographs taken at regular intervals during the processes of freeze-thaw experiments on a cryomicroscope. The images of cells are easily outlined from pictures with poor signal- to-noise ratio and the sizes of cells are computed. The results have demonstrated that this method is particularly suitable to the analysis of cell images which were taken under adverse conditions--poorly focused or in a very dusty environment, situations occurring frequently in cryomicroscopic measurement.